Adjustable transducer



Aug. 12, 1958 V w. E. BAKER 2,847,033

ADJUSTABLE TRANSDUCER Y Filed July 8. 1955 IN VEN TOR.

WILLIAM E. BAKER ATTORNEYS llnited States Patent I 2,s47,a33

ADJUSTABLE TRANSDUCER William E. Baker, Wellesley, Mesa, assignor to fitandard- Thomson Corporation, Waltham,Mass., a corporation of Delaware Application July 8, 1955, Serial No. 520,821

3 Claims. (ill. 132-788) The present invention relates to pressure-motion transducers. -More particularly, it relates to a transducer adapted for control point adjustment and provided with overtravel means.

The principal object of this invention is to provide a temperature or pressure responsive actuator of the general for-m described in the copending application of Woods, Serial No. 477,528, filed December 24, 1954, the actuator being of simple design and incorporating means for control point adjustment and for overtravel motion.

With the above and other objects in view, a principal feature of the invention resides in a construction utilizing an overtravel spring having turns at one end threaded upon an overtravel member. This member is movable in a sleeve bearing to vary the volume of a chamber having an elastomeric fill through which pressure is applied to the end of the actuator member or pin. Thus, the overtravel member cooperates with the spring to provide control point adjustment in addition to permitting overtravel movement in case of excessive applied pressures. 1

Other features of the invention include details of construction and arrangements of the parts that will be more fully understood from the following description of a preferred embodiment and from the appended drawing illustrating the same, in which Fig. 1 is a longitudinal elevation in section and Fig. 2 is a transverse sectional elevation taken on line 22 of Fig. 1.

Referring to the drawing, the invention is described as adapted for use in a remote thermostatic control. A thermal bulb 12 and capillary tube 14 form the external parts of a hermetically sealed system completely filled with a thermal liquid that remains in the same state under all normal conditions existing in storage and use. The bulb 12 is located in the space which provides the control temperature, and the capillary 14 is connected at its opposite end to an actuator 16 that is suitably mounted adjacent the device to be controlled. Control is provided through motion of a rigid metal pin 18 in relation to a fixed abutment 19 against the force of a compression spring 20 to operate a valve, to open or close electrical contacts, to actuate a mechanism, or to perform any other useful function.

The actuator has a rigid metal shell or body portion 21 having a generally conical portion defining a chamber and two generally cylindrical portions on opposite sides thereof, one being of extended length and the other of short length. The pin 18 is slidably received in an overtravel and adjustment sleeve 22 that is in turn slidably received in a sleeve bearing 23 in the body portion. The pin 18 reaches the chamber and is variably protrudable thereinto.

A flexible metallic diaphragm 24, having an annular peripheral flange and a generally flat or suitably corrugated central portion, is secured adjacent the larger end of the conical portion of the body. A rigid metal disk ice 25 is secured inside the flange and soldered thereto as indicated at 26. Alternatively, the seal between the disk and diaphragm may be accomplished by brazing or weld ing. In any event, the seal is hermetic in the strict sense, that is, an actual metallic fusion.

The disk and diaphragm are preferably assembled, filled, and sealed with the capillary 14 and bulb 12 as a subassembly. The capillary is hermetically sealed to the disk by an annular line of solder as indicated at 28, or by a weld or brazing. The subassembly is preferably filled in a chamber under high vacuum. To this end, the bulb 12 is provided with a short length of fill tube 29 which is open at the end. Under vacuum the subassembly is immersed in a body of thermal liquid that has been similarly evacuated. After filling, the fill tube 29 is crimped and soldered at the end to insure a hermetic seal.

The filled and sealed subassembly is received within the shorter cylindrical portion of the body 21, and the ends of the latter are spun over the edges of the disk 25 to hold it securely in place. It is evident that other equivalent provisions for assembly of the parts may be used, for example threaded fittings.

Preferably, the inner surface 30 of the disk 25 is slightly concave, providing freedom for the diaphragm to flex in one direction toward this surface and in the other direction toward the pin 18.

The entire space between the diaphragm 24 and the pin 18 is filled with a body of elastomeric material 32 such as rubber or a rubber-like substance, this substance being chemically stable, deformable and substantially incompressible in the pressure range anticipated for normal use.

The body 21 has a cylindrical wall 36 of slightly larger diameter than the sleeve bearing 23. Within the sleeve bearing is received the adjustment and overtravel sleeve 22. At one end the sleeve 22 lies in contact with the elastomeric body 32. Adjacent the bearing portion the sleeve has an outside threaded portion consisting of a single thread formed to receive a number of closely wound turns of a compression spring 40. These threads and the turns of the spring threaded thereonto comprise a threaded control point adjustment device hereinafter more fully described.

The spring 40 is adapted to operate in compression, having a number of spaced turns freely movable axially between the cylindrical wall 36 and the sleeve 22. With the parts assembled in the relationship shown in the drawing, the spring at) is constrained at one end by spinning inwardly the end of the body portion 21 as indicated at 42.

At the outer end of the sleeve 22 is provided an adjustment knob 44 suitably staked to the sleeve as indicated at 46.

In operation, the device is similar in many respects to that described in the previously mentioned application. The limits of pin travel are defined by the abutment 19 on the one hand, and by the position in which the diaphragm is against the wall 36 on the other hand. Within the range defined by the temperatures corresponding to these limits, the diaphragm 24 is free to deflect to allow for the volumetric expansion and contraction of the thermal liquid fill. Since the elastomeric body 32 is essentially incompressible, this body deforms and applies pressure to the end of the pin 18 which slides within the sleeve 22 to a position in which the forces acting oppositely upon the ends of the pin are equalized.

The sleeve 22 remains in fixed position relative to the body portion 21 throughout the range defined by the temperatures corresponding to the limits of pin travel. This position is determined by an outwardly turned end 48 of the spring 40, this end being axially movable within a narrow slot 50 in the body portion, but abutted against the end of the slot 50 by the force of the spring at all temperatures within this range. The strength of the spring is, therefore, greater than the force exerted by the elastomeric body 32 directly against the end of the sleeve 22 at these temperatures.

An increase in the temperature after the pin 18 reaches its outward limiting position against the abutment 19 results in a rapid increase in the pressure Within the elastomeric body 32 to produce a force sufficient to overcome that of the spring 40. In consequence, the sleeve 22 moves outwardly from the body portion 21 until it has displaced the necessary volume to compensate for the motion of the diaphragm against the substantially incompressible body 32.

Control of the temperature limits Within which the pin 18 is free to move is provided by rotation of the knob 44. The sleeve 22 is thereby turned in relation to the body portion 21, but the spring 40 does not turn by reason of its end 48 being constrained by the slot 50. Movement of the sleeve 22 within the body portion 21 produces a corresponding change in the position of the pin 18. The position of the diaphragm 22 is Wholly determined by the temperature and is not dependent on the adjustment. Since the body 32 is assumed substantially incompressible, the volume displacement produced by movement of the sleeve 22 in relation to the body 32 causes a corresponding volume displacement of the pin.

Thus, it will be seen that a device of simple construction which may be easily and cheaply fabricated has been provided. This device is essentially a pressure-motion transducer by which pressure variations on one side of the diaphragm 24 are used to produce motion of a pin 18 in relation to a fixed abutment. It is obvious that the pressure variations may be produced by other than thermal conditions, as is well understood in the art. By means of a single spring, the device provides not only overtravel protection but also means for adjustment of the temperature range corresponding to the limits of pin motion. Therefore, while the unit is capable of considerable pin motion within this temperature range, temperatures above or below the range do not build up excessive pressures within or cause damage to the device.

Having in mind the foregoing considerations, and others that will occur to one skilled in the art upon a reading of this specification, it is thus apparent that while the invention has been described with reference to a preferred embodiment thereof, such embodiment may be redesigned or modified in many ways by the skilled artisan without departing from the spirit or scope of the invention.

Having thus described the invention, I claim:

1. A pressure-motion transducer having, in combination, a shell member defining a chamber with a communicating tubular portion, said portion having a longitudinal guide therein, a hollow sleeve rotatably and slidably received in said portion and having an outside thread, a rigid pin slidably received in the sleeve, a deformable body within the chamber and lying adjacent the pin and sleeve, means to apply pressure to displace said body and thereby to move the pin, an overtravel compression spring within said tubular portion and around the sleeve, one end of the spring being threaded onto the sleeve and engaged with said guide and the other end being restrained in relation to the shell, and means for adjustably rotating the sleeve Within the shell to adjust the position of the pin at a given pressure through displacement of said body, said guide preventing rotation of the spring and the shell limiting extension of the spring while permitting compression thereof.

2. A pressure-motion transducer having, in combination, a shell member defining a chamber with a communicating tubular portion, said portion having a longitudinal guide therein, a sleeve rotatably and slidably received in said portion and having an outside thread, a rigid pin slidably protruding into the chamber, a deformable body within the chamber and lying adjacent the pin and sleeve, means to apply pressure to displace said body and thereby to move the pin, an overtravel compression spring within said tubular portion and around the sleeve, one end of the spring being threaded onto the sleeve and engaged with said guide and the other end being restrained in relation to the shell, and means for adjustably rotating the sleeve within the shell to adjust the position of the pin at a given pressure through displacement of said body, said guide preventing rotation of the spring and the shell limiting extension of the spring while permitting compression thereof.

3. The pressure-motion transducer having, in combination, a shell member defining a chamber with a communicating tubular portion, said portion having a narrow relieved channel parallel with the axis of said portion, a sleeve rotatably and slidably received in said portion and having an outside thread, a rigid pin slidably protruding into the chamber, a deformable body Within the chamher and lying adjacent the pin and sleeve, means to apply pressure to displace said body and thereby to move the pin, an overtravel compression spring within said tubular portion and around the sleeve, one end of the spring being threaded onto the sleeve and having a portion extending into said channel and the other end being restrained in relation to the shell, and means for adjustably rotating the sleeve within the shell to adjust the position of the pin at a given pressure through displacement of said body, said channel preventing rotation of the spring and the shell limiting extension of the spring while permitting compression thereof.

References Cited in the file of this patent UNITED STATES PATENTS 836,811 Kennebrew Nov. 27, 1906 2,208,149 Vernet July 16, 1940 2,534,497 Albright Dec. 19, 1950 FOREIGN PATENTS 531,280 Great Britain Jan. 1, 1941 702,868 France Jan. 27, 1931 

